As is known, perfluoropolyethers having a viscosity from 150 to 2,000 cSt (at 20.degree. C.) are utilized as lubricants since they are endowed with good characteristic properties, for example, chemical and thermal resistance, wetting power and lubricating power.
Said properties render the perfluoropolyethers suited to be employed also in extremely thin films, of the order of tens of hundreds of .ANG., as surface protecting agents.
For particular uses, as lubricants for recording media, either magnetic tapes or magnetic discs, the perfluoropolyethers are usually applicated starting from 1,1,2-trichlorotrifluoroethane solutions. This application method does not permit to obtain high-quality homogeneous and continuous films, which is an essential characteristic in order to obtain magnetic surfaces protected from surface wear, which, therefore, maintain unaltered their store capacity for a long time, nor it permits to protect the reading heads. These media, in fact, due to their operating system, are subject to the risk of abrasions due to rubbing of the head on the magnetic surface.
The non-homogeneity and non-continuity of the films are influenced by various factors, such as e.g. the rapid evaporation of the solvent utilized during the film deposition step.
The methods usually employed to obtain thin films of perfluoropolyethers consist, in fact, in spraying onto the surface to be protected, a solution of perfluoropolyether dissolved in suitable solvents, or in putting the magnetic media into said solution, or in distributing said solution onto the disc by centrifugation. 1,1,2-trichlorotrifluoroethane is generally used as a solvent, and solutions with a concentration below 10% by weight of perfluoropolyether, preferably from 1 to 5% by weight, are utilized.
After the deposition of the solution, it can follow the solvent evaporation step and the homogenization step of the residual lubricating layer by rubbing of the surface.
Furthermore, the mechanical stresses which the magnetic tapes are subjected to during their winding up, or the centrifugal force which the discs are subjected to during their operation, tend to further reduce the film homogeneity and continuity, since they cause lubricant migration phenomena with consequent thinning and breaking of the film.